PROJECT SUMMARY/ABSTRACT BACKGROUND: Working memory (WM) is the limited information retained in an active state for use in ongoing cognition. Improvements in WM from 6-14 years are critically important for how children do diverse cognitive functions like reasoning, problem-solving, and language. When teaching children (typical or challenged), little is known about how to take into account WM limits because we do not yet understand what factors contribute to typical WM development. Research by the P.I. under Grant R01-HD-21338 shows that accounts of WM development that have been proposed are insufficient (e.g., improvement in ignoring distraction or in item familiarity). We have shown this using methods in which the factors in question were experimentally controlled in new ways (e.g., capacity growth was observed independent of any distraction or familiarity effects). In my theoretical framework, WM capacity limits come from how many items can be retained concurrently in the focus of attention with enough detail to guide responses. In a new developmental hypothesis within that account, the number of WM items may remain fixed but WM develops in the richness of features within items and patterns noticed across items. Older children and adults would use features and patterns to minimize the need for attention to WM items. The RESEARCH GOAL is to assess this hypothesis with variants of new dual-set (e.g., visual+acoustic) recognition tasks, to identify roles of attention, patterns, and features in typically developing children and young adults. SPECIFIC AIMS are to uncover these bases of WM development in four ways. (1) We assess whether it is not just the number of items or objects in WM that increases in development, but the completeness of their feature representations. (2) Inasmuch as our previous work demonstrated the importance of general attention to retain information in WM, we explore a factor that may free up attention in more mature participants. Older children may engage in rapid pattern formation and memorization to ?off-load? materials out of the focus of attention, freeing attention for subsequent input and WM maintenance. We examine whether extra structure in the material allows younger children to off-load more like older ones do. (3) We recently found that off-loading occurs for acoustic and verbal lists (words or tones) much more than for visual arrays, reducing interference between acoustic items and other items. We will investigate the basis of these intriguing findings. Possibly, sequential lists of colored spots, like acoustic sequences, will allow better off-loading than do arrays of spots. We also will examine whether vibrotactile sequences compete with visual objects for attention, more than do acoustic items. Last, (4) we adopt experimental techniques from recent adult work to determine whether attention-dependent and attention-free mechanisms both develop similarly in terms of a) an increased numbers of items in WM, or b) increased item precision; their mechanisms may differ. IMPACT: How cognition should be engaged in educating children and addressing learning disorders depends on basic mechanisms of WM development, which we must uncover.